My knowledge is not even 1/5th pf usman and ahmad bhai but according to my personal observation, royal shield is a cheaply manufactured paint "Paalish". The people who apply it dont do any base prep and directly rub it on the body with a rotary at crazy speed. Then they claim at least 3 years of service life althogh the water beading lasts only ~9months.
The looks arent that great either. It gives a stupid plasticky shine which i personally do not like. If you try wolfgang sealant which is a premium product at a much lesser price, you will notice that it gives a carnuaba-likewarm shine with rich, deep reflections.
Please correct me if im wrong:D